Treatment outcomes and influencing factors of photodynamic therapy in extramammary Paget’s disease: a retrospective analysis of 31 cases

Background Extramammary Paget’s disease (EMPD) is a rare intraepithelial adenocarcinoma for which surgical excision often causes functional/cosmetic impairment. Photodynamic therapy (PDT) offers a noninvasive alternative, but data on its efficacy and influencing factors remain limited.Objective To evaluate efficacy of 5‑aminolevulinic acid (ALA)‑PDT monotherapy for localized EMPD over one year, and identify baseline predictors of response.Methods This retrospective study included 31 patients with histologically confirmed localized EMPD treated with ALA‑PDT alone. Responses were assessed at 3, 6, and 12 months. Objective response rate (ORR), disease control rate (DCR), and associated response factors were analyzed by Fisher’s exact test.Results At 3 months, ORR was 90.3% (28/31) and DCR 100% (31/31), with no complete responses (CR). At 6 months, CR was 19.4% (6/31), ORR 67.7% (21/31), DCR 83.9% (26/31). At 12 months (n = 30), CR remained 19.4% (6/30), ORR declined to 36.7% (11/30), and DCR to 56.7% (17/30). Lesion diameter ≤5 cm and absence of exudation predicted better 6‑month response (p = 0.020 and p = 0.006); diameter ≤5 cm remained significant at 12 months (p = 0.002).Conclusions ALA-PDT monotherapy achieves high short‑term responses in localized EMPD, but efficacy declines substantially by 12 months. Lesion diameter ≤5 cm and non-exudative morphology predict better responses.